1. Field of the Invention
The present invention concerns freewheel devices.
2. Description of the Prior Art
Freewheel devices generally include an outer ring provided with a cylindrical inner slideway for cams of the freewheel, an inner ring or a shaft provided with a cylindrical outer slideway for said cams of the freewheel, and a freewheel disposed between the slideway of the outer ring and the slideway of the inner ring or shaft.
The freewheel includes a single cage or a double cage consisting of two concentric cages, provided with windows in which are disposed cams which provide a unidirectional coupling between the outer and inner rings by being wedged or by sliding between the two slideways.
The cage generally has a radial flank imparting sufficient rigidity to the cage on at least one side.
The freewheel is therefore able to transmit a torque between the outer and inner rings in one direction and to allow free rotation in the other direction.
To encourage tilting of the cams in the wedging direction, a spring can be provided in the form of a strip exerting on each cam a return torque tending to hold the cams at all times in contact with the slideways.
These freewheel devices are used in automobile automatic transmissions in particular.
To improve the working of freewheel devices and/or to facilitate their assembly, devices for frictionally linking the outer ring of the freewheel and the cage have been envisaged.
The documents FR-A-2 474 121 and EP-A-0 641 948 disclose radially elastic members cut out from the cage and coming into contact with the bore of the outer ring. These devices operate satisfactorily. However, according to the document FR-A-2 474 121, bent strips are used, which must therefore be bent, which is a supplementary operation of non-negligible cost. The strips, because of their small section, are also relatively sensitive to impact, which necessitates a few precautions in connection with packaging and handling them.
The cage according to the document EP-A-0 641 948 necessitates a cutting operation on elastic parts which must be performed as a final reworking of the cage when it has already been formed to shape, which increases manufacturing time and leads to a relatively high manufacturing cost. Also, some portions of the cage, especially in the cylindrical part provided with the cam cells, are deformed and the overall rigidity of the cage is degraded, which can compromise correct working of the freewheel in some circumstances.
The present invention proposes to solve the problems referred to above.
The present invention proposes an economic and reliable freewheel device provided with a cage enabling easy fitting of the freewheel between the slideways and holding the freewheel effectively in that position.
The invention therefore proposes a freewheel device including at least one cage, a plurality of wedging members retained by the cage, and a member having a cylindrical surface adapted to come into contact with the cage, which has an axial portion provided with windows adapted to receive immobilizing members and at least one generally annular and substantially radial portion having a flexing area and a plurality of tongues of substantially radial shape in a relaxed state and adapted to flex in an axial direction so that ends of the tongues are in frictional contact with the cylindrical surface so that they are circumferentially and axially connected to the surface.
In one embodiment of the invention the flexing area is thinner than the remainder of the substantially radial portion.
The flexing area can be near the axial portion, i.e. nearer the axial portion than the free ends of the tongues. The flexing area can be in the immediate vicinity of the axial portion in the radial direction.
The flexing area can be radially between the ends of the tongues and the axial part.
The tongues can be generally trapezoidal. The cage can be made from sheet-metal, for example from steel plate.
In one embodiment of the invention the cage has an L-shaped section with an axial portion and a radial portion.
In another embodiment of the invention the cage has a U-shaped section with an axial portion and two radial portions. One radial portion can have a supplementary portion. Both radial portions could have a supplementary portion.
The freewheel can further include a spring to encourage tilting of the wedging members.
The member is advantageously a bore of an outer ring or an outside surface of an inner ring or a shaft.
The tongues can be oblique when mounted.
The tongues preferably prohibit by means of wedging effect axial movement in at least one direction relative to the member having a cylindrical surface in contact with the cage.
The member advantageously has a bevel at one end of the cylindrical surface. The bevel facilitates mounting the cage on the cylindrical surface.
In one embodiment the member has a shoulder at the other end of the cylindrical surface to form an axial abutment for the cage which is therefore retained in one direction by the axial abutment and in the other direction by friction between the free ends of the tongues on the cylindrical surface and the wedging effect of said supplementary portion.
The invention also proposes a method of manufacturing a freewheel cage, wherein the flexing area is formed at the same time as the substantially radial portion.
The flexing area and the substantially radial portion are advantageously formed in the same operation.
Thus the cage is provided with means providing a circumferential and axial friction connection with one of the rings of the freewheel. Those means prevent axial movement of the cage relative to the ring during assembly.
The invention will be better understood after studying the following detailed description of a few embodiments of the invention, given by way of non-limiting example only and shown in the accompanying drawings.